Methods

posixArgvParser.create()

Creates a new instance of posix-argv-parser that holds a collection of
options and operands.

args.createOption(flags[, options])

args.createOption(["-h","--help"]);

Creates a new option. An option has all the properties of an
argument, as well as option.hasValue and option.timesSet. The
options object is optional.

args.addShorthand(opt, [argv1, ...])

A shorthand is a convenience method for adding options to your CLI
that simply set other options.

args.createOption("--env",{ hasValue:true});

args.addShorthand("--dev",["--env","dev"]);

args.addShorthand("--prod",["--env","prod"]);

This makes passing --dev an equlvalent to passing --env dev.

args.createOperand([name][, options])

args.createOperand();

Creates a new operand. An operand has all the properties of an
argument, as well as greedy: true|false - i.e. whether or not it
will eat many arguments or just one (defaults to false, just one).
The name is optional, and should be a string. The name is used to
access the value through the options object passed to the parse
callback. If not provided, it defaults to "OPD" (beware when using
more than one operand).

args.parse(args, callback)

Performs parsing and validation of argv. In Node.JS, make sure to discard
the first two items of process.argv, as they
contain unrelated arguments ("node" and the file name).

The callback is called with two arguments, errors, which is either
undefined, or an array of errors and/or validation messages, and an
options object, which is used to retrieve data from configured options.

var args =require("posix-argv-parser").create();

args.handle(process.argv.slice(2),function(errors,options){

if(errors){

// Print an error msg, i.e. console.log(errors[0])

return;

}

// Continue with normal operation. I.e. options["-v"].hasValue,

// options["-v"].timesSet, options["-p"].value, etc.

});

Arguments (options and operands)

Options (args.createOption and operands (args.createOperand) are
the two types of arguments handled by posix-argv-parser, and they
share common functionality, listed below this introduction.

An option is a flag, with or without a value. -p, -p abc,
-pabc, -p=abc, --port abc and --port=abc are all supported by
posix-argv-parser.

-pabc can mean both -p -a -b -c and -p=abc. posix-argv-parser
uses opt.hasValue to separate the two. With opt.hasValue set to
true, -pabc will be handled as -p=abc. When false (default), it
will be handled as -p -a -b -c. In that case you also need to have
option handlers for -a, -b and -c, or you'll get a validation
error such as "unknown option -a" (depending on which option
posix-argv-parser first encountered that didn't exist).

An operand is an option-less value, i.e. foo (with no -b or
--myopt prefixing it). It's commonly used for arguments that always
have to be passed. Examples are nano path/to/file.txt, git checkout master, rmdir my_dir, etc. The validators validators.file,
validators.directory, and validators.fileOrDirectory are very
useful for operands.

Note that the parser can handle a mix and match of options and
operands in any order, i.e. mycommand --port 1234 my/directory and
mycommand my/directory --port 1234 will both work.

Multiple operands will be applied in order of creation. I.e.
mycommand something with two operands will assign "something" to
the first and undefined to the second, unless the first is greedy,
in which case it will receive all the operand values.

See example usage at the beginning of this document for more
information.

When creating options and operands, the following properties can be
passed in with the "options" object.

opt.validators

An array of validators. A validator is a function that accepts the
argument result object as input. See below for a description of
argument result objects. To fail validation, the validator can either
throw an error, or return a rejecting promise.

opt.transform

A function that transforms the raw string value provided before
assigning it to the opt.value property of an argument result object.
The function receives the string value as input, and should return any
value back.

opt.hasValue

If the argument takes a value, set to true. Defaults to false for
options, is always true for operands (thus it can be omitted).

opt.defaultValue

The default value to use if the argument was not provided. When
opt.defaultValue is provided, opt.hasValue is implied
and can be omitted. The default value should be a string, and will be
validated and transformed like actual values.

opt.signature

The signature is used to identify options and operands in validation errors.
Options automatically gets a signature consisting of the option flags assigned
to it::

var opt =args.createOption(["-v","--version"]);

opt.signature;// "-v/--version"

opt.signature="-v";// custom signature

Specifying a signature is more useful for operands, since an operand doesn't
have any data that it can use to auto generate a signature (their default signature
is "OPD").

var rootDir =args.createOperand();

rootDir.signature;// "OPD", as the default name

rootDir.signature="Root directory";

Options

Options has additional properties that operands doesn't have.

opt.requiresValue

Only makes sense if opt.hasValue is true. When this property
is false, an option can both be provided as a flag with no value or
as an option with a value.

A common example of options that work with and without values are help
options, that may be provided alone to get general help, e.g. mything --help, and with values to get help for specific topics, e.g.
mything --help bisect.

Argument result

Argument result objects are produced when calling args.parse to
parse argv into the predefined options and operands. There is one
result object per original option/operand. These objects have the
following properties:

argumentResult.isSet

true or false depending on whether or not the argument was present
in argv.

argumentResult.value

The value of the argument. Is normally a string, but may be any object
if the argument had a transform function.

argumentResult.timesSet

The number of times an argument was set. Useful for options like -v
(verbose) which you might want to allow setting multiple times, giving the
user more and more verbose output from your program:

-v // 1

-vv // 2

-v -v -v -v // 4

-v -vv -vv -vvv // 8

Validators

Validators let you add requirements with associated error messages to
options and operands.

posix-argv-parser has a number of built-in validators, and creating
custom ones is dead simple, as a validator is just a function.

Built-in validators

The built in validators provides a selection of generic validators.
You can customize the error messages by passing strings with tokens
like "${1}" in them. The number and value maps are documented for
each validator.

Validators are functions, yet the built-in validators are used by
calling them directly with custom error messages. This works because
the built-in validators all return the actual validation function.

// Uses built-in error message

posixArgvParser.validators.required();

// Specify your own error message

posixArgvParser.validators.required("${1} has to be set");

validators.required(errorMessage)

Fails if the option is not set.

Custom error message:

${1}: The option opt.signature

validators.integer(errorMessage)

Will fail validation if the option was not an integer, i.e. "foo"
and 42.5.

Custom error message:

${1}: The specified number
${2}: The option opt.signature

validators.number(errorMessage)

Will fail validation if the option was not a number, i.e. "foo" and
?.

Custom error message:

${1}: The specified number
${2}: The option opt.signature

validators.file(errorMessage)

Will fail validation if the option was not a path pointing to an
existing file in the file system.

Custom error message:

${1}: The specified file
${2}: The option opt.signature

validators.directory(errorMessage)

Will fail validation if the option was not a path pointing to an
existing directory in the file system.

Custom error message:

${1}: The specified directory
${2}: The option opt.signature

validators.fileOrDirectory(errorMessage)

Will fail validation if the option was not a path pointing to an
existing file or directory in the file system. Will fail for block
devices, sockets, etc.

Custom error message:

${1}: The specified file or directory
${2}: The option opt.signature

Custom validators

A validator is a function that throws an error or returns a promise.
If it does not do any of those things, it is immediately considered
passed. The function is passed an argument result object.

args.createOption("-v",{

validators:[function(opt){

if(opt.value=="can not be this value"){

thrownewError("This is the error message.");

}

}]

});

Promises are used to facilitate asynchronous validators. Here's an
example of a validator that checks if a file is larger than 1MB::

var when =require("when");

args.createOption(["-f"],{

validators:[function(opt){

var deferred =when.defer();

fs.stat(opt.value,function(err,stat){

if(err){deferred.reject("Unknown error: "+ err);}

if(stat.size>1024){

deferred.reject(opt.value+

" ("+opt.signature+") was larger than 1MB");

}else{

deferred.resolve();

}

});

returndeferred.promise;

}]

});

Given --myopt /path/to/file and the file is larger than 1MB, you'll
get the error message "/path/to/file (--myopt) was larger than 1MB".

Rejecting the promise counts as an error. The first argument should be
a string, and is the error message. (TODO: This will likely change to
an error object with a message property).

Transforms

Transforms can mutate the values of options. A transform is a simple
function that receives the raw string value as input, and can return
whatever it likes.::

args.createOption(["-p"],{

transform:function(value){returnparseInt(value,10);}

});

Types

Types are predefined "options" objects that you can pass when creating
options and/or operands. For instance, the "number" type includes the
number validator, sets opt.hasValue to true, and includes a
transform that converts the raw string to an actual number (by way of
parseFloat)::

args.createOption(["-n"],args.types.number());

Note that the type is a function call - it returns the options object.
You can pass in additional options. The following example piggy-backs
the number type to create an option that only takes positive numbers::

args.createOption(["-n"],args.types.number({

validators:[function(opt){

if(parseFloat(opt.value)<0){

thrownewError("Oh noes, negative number!");

}

}]

}));

Providing --help

It's not in the nature of posix-argv-parser to automatically handle
--help for you. It is however very easy to add such an option to
your program. To help you keep all CLI option data in one place,
options and operands are allowed to have a opt.description
property that posix-argv-parser does not care about::